Geological Deformation: Fast vs. Slow Processes and Impact on Mountain Building, Slides of Earth Sciences

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Deformation Rate

•

Rapid deformationrequires higherstress to cause thedeformation

Rapid deformationfavors brittlebehavior - Faulting is rapid - General mountain-building is muchslower Stress^ Stress Strain^ Strain

Behavior of Silly Putty

Experimental Method

Maximum Pressure^ Maximum Pressure Minimum Pressure^ Minimum Pressure Squeezing makes^ Squeezing makesthe cylinder get^ the cylinder getshorter and fatter^ shorter and fatter

Testing Rocks

60°^60 ° 60°^60 °

Experimental Deformation

Where Does Deformation Occur?

•

Tensional Deformation

• Pulling apart – Environments where the crust is being stretched – Divergent margins—mid-ocean ridges and continental rifts - Compression - Convergent margins – Subduction zones – Continent-continent collisions

Where Does Deformation Occur?

• Shear

• Where the plates slide past each other – On faults of any kind

• Deformation generally takes place in

orogens

• Elongated region of the crust that has been deformed and metamorphosed bycontinental or sub-continental collisions

Cratons and Orogens

Why are Mountains?

• Some lingering questions

• Why do mountains rise so high? – Why don’t mountains wear down more rapidly? - Why are ocean basins so low? – How stable is the crust? – How ductile is the mantle?

• What about vertical motion?